The cooling system helps regulate the amount of heat in the engine.
Your car’s engine runs most efficiently at a relatively high and steady temperature. If it’s too hot, the engine can overheat. If it’s too cold, the engine emits more pollutants, and components prematurely wear out. If the cooling system fails to keep the engine at the right temperature, it can suffer significant damage and in some cases, fail entirely.
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Coolant Expansion Tank
Cooling Fan Motor
Cooling Fan Assembly
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Radiator hose - lower
Radiator hose - upper
Although a few cars are air-cooled, most modern vehicles use liquid cooling. Here are the critical components in liquid-cooled systems.
Coolant, or antifreeze, performs two critical function: keeping radiator fluid from freezing in wintry conditions and keeping the engine from overheating in the summer. Coolant is composed of 50 percent ethylene glycol and 50 percent water, which helps raise its boiling point and lower its freezing point. Corrosion inhibitors protect vital metallic cooling system components from corroding, and silicates lubricate seals. There are different kinds of antifreeze, which are most easily identified by their color. How do they differ?
"The green stuff” is the traditional coolant, which can be used in most cars. It contains lubricating silicates and corrosion inhibitors, but these silicates deteriorate rather quickly, requiring coolant changes every 2 years or 24,000 miles.
Coolant can also be red, yellow, orange, or even purple. Most coolants not green in color are similar: they are simply dyed different colors. They have a longer claimed service life, thus requiring fewer fluid changes—in some cases up to 100,000 miles. Refer to your owner’s manual for details on your car’s coolant requirements.
The radiator is a heat exchanger with hundreds of individual tubes and fins that reduce the temperature of the coolant. As coolant travels through the engine passageways, it absorbs and removes heat from the engine, transporting it to the radiator. Air flows through the coolant passages as the car moves, cooling the tubes and fins, and coolant reenters the engine with a reduced temperature.
Radiator cap. If you’ve ever worked on a car, then you know not to remove the radiator cap while the engine is warm. That's because the cap is a pressure-release valve. It also keeps the cooling system under pressure to increase the boiling point of coolant.
The engine, or radiator, fan can be driven by a drive belt or an electric motor. It helps cool a car when it is stationary or moving slowly.
The thermostat helps the engine reach operating temperature by preventing coolant from circulating to the radiator, thus allowing the engine to heat up more quickly. As the engine reaches operating temperature, the thermostat opens and allows coolant to flow through the radiator.
The water pump circulates coolant through the system via an impeller (a rotor that spins to move fluid) that is driven by a belt.
The heater core is a smaller version of the radiator located underneath the dashboard. A motor blows air past the heater core, which transfers heat to the air. This keeps cabin occupants warm even in winter.
Transmission cooler. In addition to keeping the engine cool, on cars with an automatic transmission the radiator is equipped with a separate heat exchanger to keep transmission fluidfrom boiling over.
If your car is leaking coolant, immediately determine from where and how much. If it continues to leak, schedule your car for service as soon as pos